1920, “Two Pictures on a Single Canvas”, in Technology Review, page 579:
This is the fact of a new and vitally interesting experiment in the realm of physics, psychology, and art. There is no trick to this, as tricks go, except the mathematical magic of simple physics. Of course, simple physics for one man is black magic for another.
1970, Charles Nasem, The National Center for Law Information concept: a discussion, page 16:
The NCFLI will provide a step-by-step explanation of the processes involved. This should be done in order to dispel, to the extent possible, the notion that computerized production of legal texts and reports is "black magic," or that a hard copy of the processed text is something quite mysterious.
When referring to technology, calling something (plain) magic means that it is not widely understood, but suggests it can be understood by those versed in the field. Black magic suggests few understand it.